<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>表单</title>
        <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

    </head>
    <body>
        <div ></div>
        <form action="">

            <div>
                <span>用户名</span>
                <input  type="text" placeholder="your email">
            </div>

            <div>
                <span>密码</span>
                <input type="password">
            </div>

            <div>
                <button type="submit" class="btn btn-primary"> login</button>
            </div>
            <div class="yejiao"></div>
        </form>
    </body>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
</html>